(Image credit: @yokoono/Twitter)

Yoko Ono joined the U.S. gun debate when she tweeted a picture of the blood-stained glasses her husband, John Lennon, was wearing when he died. Lennon, one of the Beatles, died in 1980 after being shot in the back four times at the couple's New York City apartment by a crazed stalker. He was pronounced dead on arrival at St. Luke's Roosevelt Hospital.

The blood-spattered glasses in the image included text that brought attention to the number of people who have died from gun violence since her husband's death. The tweets were sent Wednesday morning in commemoration of what would have been her and Lennon's 44th wedding anniversary.

Ono tweeted the image four times, including different anti-violence reflections each time, saying that guns are making America into a "war zone."

She also urged her followers to "bring America back" to a "green land of peace."

Ono, 80, concluded her succession of tweets by saying that in the 33 years after Lennon's death, she and the couple's son, Sean, 37, still miss him.